If corrected serum calcium is > 2.75 mmol/l at any time, hold calcitriol for one week and repeat laboratory test for calcium. If the subject's next serum calcium is < 2.62 mmol/l, calcitriol may be restarted at 0.25 mcg twice weekly. If the next serum calcium level is > 2.62 mmol/l, the subject will be discontinued from the study.